US Attorney General Eric Holder speaks at a news conference in Washington Friday. The accused mastermind of the September 11 attacks and four other top terrorism suspects held at Guantanamo Bay will prosecuted in US criminal courts, Holder said, the first major step in their bid to close the controversial prison.

The self-described mastermind of the 9/11 terror attacks, Khalid Sheikh Mohammed, and four alleged co-conspirators have been designated to stand trial in a federal courtroom in New York City.

The announcement on Friday touched off an immediate and heated debate over the potential implications of the move. Attorney General Eric Holder called it "the toughest decision I've had to make as attorney general."

In rejecting the option of trying the five men before a military commission, the Obama administration is setting the stage for a potentially historic trial in a civilian courthouse just a short walk from the empty skyline where the World Trade Center's twin towers once stood.

The move represents an assessment by Attorney General Holder that the harsh treatment meted out by US intelligence officers during prolonged interrogations – including waterboarding – will not prevent federal prosecutors from producing enough taint-free evidence to win convictions.

But the move carries risks, legal analysts say. It opens the door to aggressive defense tactics that will seek to put the US government itself on trial for alleged lawless kidnappings and interrogations. It will trigger an array of fundamental constitutional challenges – including an argument that the last place on earth the 9/11 conspirators can receive a fair trial is New York City.

Perhaps more important, analysts say, it carries risks that a trial in an open New York courtroom could provide an international stage for Mr. Mohammed to portray himself to the Muslim world as a hero and martyr who has endured torture and injustice at the hands of the US government in service to Islam. A guilty verdict and death sentence under those circumstances would only enhance his standing among some Muslims.

The challenge in the trial for the Obama administration will be to overcome Mohammed's claims of martyr status by showing the world the true face of a mass murderer, analysts say.

This is the mission Holder announced on Friday.

"After eight years of delay, those allegedly responsible for the attacks of September 11 will finally face justice," the attorney general told a press conference in Washington.

More trials at Guantánamo

In announcing the decision to bring Mohammed and four others to New York, Holder also said the administration had designated five other Guantánamo detainees to stand trial before military commissions.

Holder said the administration has not yet decided where the military commissions will be conducted.

The announcements were made as part of a high-priority effort to make good on President Obama's pledge to close the Guantánamo detention camp by Jan. 22. But that pledge looks increasingly unlikely.

Holder repeated his skepticism that the deadline will be reached. He said the primary delay has been finding countries willing to accept detainees designated for transfer. Estimates are that as many as 90 of the current 215 detainees at Guantánamo have been approved for transfer.

Possibility of acquittal

The attorney general was asked whether he is concerned that Mohammed or other terror suspects might be acquitted.

"I would not have authorized the prosecution of these cases unless I was confident that our outcome would be a successful one," he said. Holder added that he has access to information that has not yet been released publicly that leads him to believe the prosecutions will be successful.

Although the case will be tried in federal court in lower Manhattan, the prosecutors are being drawn from both the Southern District of New York and the Eastern District of Virginia. Both districts have had experience with high-profile terrorism trials.

It is unclear when Mohammed and the others will be physically transferred to the US from Guantánamo. Federal law requires the administration to give Congress a 45-day notice of any potential transfer. In addition, the case against Mohammed and the others must be presented to a federal grand jury in New York. Holder told the press to expected indictments "relatively soon."

He added: "They will be charged with what we believe they did; that is to mastermind and carry out the 9/11 terrorist attacks."

Prosecutors seek death penalty

Holder said the government will seek the death penalty for all five defendants.

Asked if he believed Mohammed and the others can receive a fair trial in New York City, Holder said a careful examination of each prospective juror by the trial judge would be able to ensure a fair trial.

The attorney general dodged questions about what might happen in the event of an acquittal. He repeatedly answered that he did not expect an acquittal.

But the US government retains another option. The Obama administration has made clear that it intends to continue the Bush administration's policy of indefinitely detaining without charge individuals it deems are too dangerous to be set free.

Under this regime, an acquitted suspect could be moved back into open-ended military detention, legal analysts say.